Conventional methods of reducing interference between multiple sonar pulses suffer from several limitations. One method utilizes a system that interconnects and synchronizes multiple same-frequency sonic sources that operate in close proximity to each other. The sonic sources are configured in a master-slave relationship. The master sonar unit functions as a controller that synchronizes the simultaneous firing of all the connected slave sonar units.
This method suffers from several disadvantages. First, a relatively sophisticated control communication network is required between the master and the slave units. This control communication network introduces delay between the signals reaching the different sonar units. Any delay in the signals reaching the different sonar units will cause the sonar units to generate sonar pulses which are not completely synchronized.
Second, the control communication network adds a level of complexity to the system as a whole and, moreover, to the cost of the system. Third, in this configuration, each sonar unit is utilizing its own pulse generator to send the signal to each transducer, thus adding a level of uncertainty in the synchronization of the sonar units, as well as to the overall cost. Fourth, the method can only be utilized with sonar units that transmit sonar pulses of the same frequency.
Another method used in radar systems utilizes a pulse trigger signal for synchronizing multiple radar systems operating in the same area. Subsequently the different radar systems generate radar pulses in accordance with pre-determined operating parameters (such as carrier frequency at which the radar pulses are transmitted and carrier frequency offset with respect to carrier frequencies used by other radar systems) and the synchronization provided by the pulse trigger signal.
One disadvantage of this method is the complexity and the cost of the system. Once again, another disadvantage is the potential delay that could be introduced by the pulse trigger signal and cause radar/sonar unites to generate radar/sonar pulses which are unsynchronized.